In Situ High-Temperature Synchrotron Diffraction Studies of (Fe,Cr,Al)₃O₄ Spinels

Abstract

The modeling of a loss-of-coolant-accident scenario involving nuclear fuels with FeCrAl cladding materials in consideration to replace a Zircaloy requires knowledge of the thermodynamics of oxidized structures. At temperatures higher than 1500 °C, oxidation of FeCrAl alloys forms (Fe,Cr,Al)3O4 spinels. In situ high-energy X-ray diffraction in a conical nozzle levitator installed at beamline 6-ID-D of the APS was used to study the structural evolution of the oxides as a function of the temperature. Single-phase (spinel) and multiphase (spinel–corundum–FeAlO3) regions are mapped as a function of the temperature for three different compositions of FeCrAl oxidation products. The thermal expansion coefficients and cation distribution in the spinel structure have been refined. The temperature at which complete melting of the fuel cladding is expected has been determined by the liquidus temperatures of the oxidized products to be between 1657 and 1834 °C in a 20% O2/Ar atmosphere using the cooling trace method. The liquidus temperature increases with increasing Al and Cr content in the spinel phase.

In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides

“…At those temperatures, there is a mixture of H- and X-type phases, and the H-type phase is richer in smaller REs than the X-type phase. Such deviation from linearity for lattice parameter values at phase-transition temperatures is a common phenomenon. − The X-type phase was observed in only two diffraction patterns, and its lattice parameter increased from 4.37397 Å at ∼2300 °C to 4.3807 Å at ∼2350 °C.…”

Crystal growth and phase formation of high‐entropy rare‐earth monoclinic aluminates

“…One strategy to perform these measurements is to use a containerless sample environment. Aerodynamic levitation and laser heating have been previously used to perform high‐temperature neutron and XRD on high‐entropy oxides 24,41,43–47 …”

“…Aerodynamic levitation and laser heating have been previously used to perform high-temperature neutron and XRD on high-entropy oxides. 24,41,[43][44][45][46][47]…”

Considerations for quantitative in situ X-ray powder diffraction studies of solid-state reactions

“…Quantitative phase analysis of powder X-ray diffraction (PXRD) data collected in situ, as a reaction occurs, is increasingly being used to evaluate how the abundance of reagent, intermediate and product phases evolve and to gain insight into the reaction kinetics and mechanism. By comparing how a reaction evolves at different temperatures, with different chemical precursors and for different stoichiometries, we can develop an understanding of what governs reaction progress (Agca et al, 2020;Chen et al, 2011;Wu et al, 2015) so that, ultimately, we can design reactions that deliver new target materials with optimal yield, purity and cost (Wicker & Walker, 2013;Martinolich et al, 2016;Todd et al, 2020;Shoemaker et al, 2014).…”